flowchartsman opened a new issue #8769:
URL: https://github.com/apache/pulsar/issues/8769
**Describe the bug**
Go functions with the signature `func contextFunc(ctx context.Context, in
[]byte) ([]byte, error)` crash on attempting to discard the message by
returning nil.
**To Reproduce**
Create a pulsar function with the following code:
```go
package main
import (
"context"
log "github.com/apache/pulsar/pulsar-function-go/logutil"
"github.com/apache/pulsar/pulsar-function-go/pf"
)
func contextFunc(ctx context.Context, in []byte) ([]byte, error) {
log.Info("attempting to discard input")
return nil, nil
}
func main() {
pf.Start(contextFunc)
}
```
Deploy: `pulsar-admin functions create --name test --namespace default --go
<path to function binary> --inputs test --output test.out`
```
2020/12/01 13:49:50.490 main.go:11: [info] attempting to discard input
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0xb06313]
goroutine 1 [running]:
github.com/apache/pulsar/pulsar-function-go/pf.(*goInstance).ackInputMessage(0xc0002a72c0,
0xd85c20, 0xc000416000)
/<home
dir>/go/pkg/mod/github.com/apache/pulsar/[email protected]/pf/instance.go:361
+0x73
github.com/apache/pulsar/pulsar-function-go/pf.(*goInstance).processResult(0xc0002a72c0,
0xd85c20, 0xc000416000, 0x0, 0x0, 0x0)
/<home
dir>/go/pkg/mod/github.com/apache/pulsar/[email protected]/pf/instance.go:352
+0x85
github.com/apache/pulsar/pulsar-function-go/pf.(*goInstance).startFunction(0xc0002a72c0,
0xd6e8a0, 0xc00003c740, 0x0, 0x0)
/<home
dir>/go/pkg/mod/github.com/apache/pulsar/[email protected]/pf/instance.go:176
+0x58e
github.com/apache/pulsar/pulsar-function-go/pf.Start(0xb9a360, 0xcb9340)
/<home
dir>/go/pkg/mod/github.com/apache/pulsar/[email protected]/pf/function.go:171
+0x6b
main.main()
/<home dir>/go/src/scratch/pulsartest/cmd/brokenfunc/main.go:16 +0x39
```
**Expected behavior**
Message discarded. Function does not crash
**Additional context**
The code crashes in the following function:
```go
// ackInputMessage doesn't produce any result, or the user doesn't want the
result.
func (gi *goInstance) ackInputMessage(inputMessage pulsar.Message) {
gi.consumers[inputMessage.Topic()].Ack(inputMessage)
}
```
which is called by
[*goInstance.processResult](https://github.com/apache/pulsar/blob/7f62bbcbd687d67d5b3fd9b1bab2101e64c42c59/pulsar-function-go/pf/instance.go#L326)
in the case of a nil return in this example.
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